Functionalized exfoliated nanoclay and non-polar polymer nanocomposite compositions

ABSTRACT

Exfoliated nanoplatelets functionalized with a non-polar moiety, such as an ethylene or propylene derived polymer, are useful for forming composites, films, and polymer blends.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Application No. 62/990,326, filedMar. 16, 2020, the disclosure of which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

Nanoclay platelets have been incorporated into polymeric matrices toimprove the ability of such matrices to act as barriers to oxygen andwater. These properties are particularly useful for food packagingfilms.

Despite the advances in the development of polymeric matrices and filmsthat serve as barriers to oxygen and water, a need exists for improvedpolymeric matrices and improved nanoclay platelet compositions for thesematrices. The present invention seeks to fulfill these needs and providefurther related advantages.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a functionalized exfoliatednanoplatelet. In certain embodiments, the invention provides acomposition comprising an exfoliated nanoplatelet functionalized with anon-polar moiety. The exfoliated nanoplatelet is functionalized with anon-polar moiety to advantageously facilitate further processing of thenanoplatelet as described herein. The non-polar moiety is associatedwith platelet through a bonding interaction. As used herein, the term,“non-polar moiety” includes hydrocarbon moieties that are branched orstraight chain hydrocarbon moieties having at least about 10 carbonatoms. The length (upper limit of carbon atoms) the hydrocarbon moietycan be adjusted to suit the application. In certain embodiments, thehydrocarbon chain has at least about 12 carbon atoms. In otherembodiments, the hydrocarbon chain has at least about 20 carbon atoms.In further embodiments, the hydrocarbon chain has about 1000 carbonatoms. In other embodiments, the hydrocarbon chain has about 10,000,about 20,000, about 30,000, or about 50,000 carbon atoms. In oneembodiment, the hydrocarbon has about 35,000 carbon atoms (as measuredby GPC). In certain embodiments, the non-polar moiety is associated withthe platelet through a hydrogen bonding interaction. For example, thehydrogen bonding interaction between the amine group of ZrP/APTMS andthe ester group of PE-co-VAc.

In other embodiments, the non-polar moiety is covalently coupled to thenanoplatelet. For example, the covalent coupling of a polyethylene groupto the platelet resulting from an olefin metathesis reaction, such as aring-opening olefin metathesis reaction in the presence of a transitionmetal catalyst.

In certain embodiments, the non-polar moiety is associated with theplatelet through a silane that is covalently coupled to the platelet. Incertain of the embodiments, the lower and upper limits of the silane is1 to 70% (calculated by TGA (thermogravimetric analysis) and solid-stateNMR (nuclear magnetic resonance)). The preferred density varies based ondifferent application and the requirement 10 mol % to the POH (—P(O)OHgroups on the surface of the nanoplatelet). For the ZrP-NTES-ETMS, NTES:10 mol %, ETMS: 40 mol % to the POH.

In certain embodiments, the non-polar moiety is produced by an olefinmetathesis reaction. In certain embodiments, the non-polar moiety isproduced by a ring-opening olefin metathesis reaction in the presence ofa transition metal catalyst. In certain embodiments of theseembodiments, the ring-opening olefin metathesis reaction is a reactionbetween an alkene covalently coupled to the platelet and a cycloalkene,wherein the alkene is selected from the group consisting of a vinylgroup and cyclic and polycyclic olefins (e.g., a norbornyl group).

In the composition, the exfoliated nanoplatelet is derived from anatural or synthetic nanoclay.

In another embodiment, the invention provides a film comprising thefunctionalized exfoliated nanoplatelet as described herein.

In another aspect of the invention, nanocomposite compositions areprovided. In certain embodiments, the invention provides a nanocompositecomposition comprising a mixture the functionalized exfoliatednanoplatelet as described herein and a polymer derived from ethylene orpropylene. In certain embodiments of these embodiments, the inventionprovides a polymer derived from ethylene and/or propylene (e.g.,polyethylene (PE), polypropylene) or a copolymer derived from ethyleneand/or propylene (e.g., PE-co-PAc). In certain embodiments, theinvention provides a blend comprising the functionalized exfoliatednanoplatelet as described herein and a polymer having ethylene orpropylene units, wherein the non-polar moiety of the composition is asilane with a free amine or free hydroxy group, and wherein the polymeris modified to be absorbed to nanoplatelets by the free amine or freehydroxy group. In other embodiments, the invention provides a blendcomprising a copolymer of polyvinyl acetate and polyethylene orpolypropylene and the functionalized exfoliated nanoplatelet asdescribed herein, wherein the non-polar moiety of the composition is asilane with a free amine or free hydroxy group.

In certain embodiments, the nanocomposite composition exhibits a modulusincrease of 100% relative to the polymer containing no filler, asmeasured by dynamic mechanical analysis (DMA).

In certain embodiments, the nanocomposite composition exhibits a modulusincrease of 150% relative to the polymer containing no filler, asmeasured by tensile test.

In another embodiment, the invention provides a film comprising thenanocomposite composition as described herein.

In a further aspect of the invention, lyotropic suspensions areprovided. In certain embodiments, the invention provides a lyotropicsuspension, comprising the functionalized exfoliated nanoplatelet asdescribed herein and an organic medium (e.g., a polymer or a solvent).Representative solvents include methanol, dichloromethane, acetone,tetrahydrofuran, toluene, and xylene. Representative polymers includePE-co-VAc and polycyclooctene (PCO).

In another aspect, the invention provides methods for producing theexfoliated nanoplatelet as described herein. In certain embodiments, themethod comprises:

(a) covalently coupling a silane to an exfoliated nanoplatelet, whereinthe silane has a functional group for associating a polymer to thenanoplatelet;

(b) associating a polymer comprising a hydrocarbon-chain with at least20 carbons to the nanoplatelet through the functional group of thesilane.

In certain embodiments, the functional group of the silane is a hydroxygroup or an amine group and the polymer. In certain of theseembodiments, the polymer is associated to nanoplatelet through ahydrogen bonding interaction.

In other embodiments, the functional group of the silane is an alkenegroup (e.g., vinyl or norbornyl group). In certain of these embodiments,the polymer is associated to nanoplatelet through covalent coupling(e.g. ROMP).

In certain embodiments, the polymer comprising a hydrocarbon-chain withat least 20 carbons is a polymer derived from ethylene or propylene(e.g., PE and PE-copolymers).

In a further aspect, the invention provides a method for producing anexfoliated nanoplatelet functionalized with a covalently-bound non-polarmoiety containing a hydrocarbon-chain with at least 20 carbons, whereinthe polymer has a controlled graft density and controlled molecularweight.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings.

FIG. 1A is a schematic illustration of a representative nanoplateletfunctionalized with an alkoxysilane having a free amine (APTMS).

FIG. 1B is a schematic illustration of the preparation of arepresentative nanocomposite of the invention, PE-co-VAc/ZrP, fromnanoplatelet functionalization with an alkoxysilane having a free amine(APTMS).

FIG. 2 is a schematic illustration of the interaction between PE-co-VAcwith the free amine of the silane covalently coupled to the nanoplateletfor the nanocomposite shown in FIG. 1A.

FIGS. 3A-3D compare of rheology properties containing well-exfoliatedZrP (ZrP-APTMS) and intercalated ZrP (ZrP-M1000): complex viscosity(3A), storage modulus (3B), and Tan δ (3C). FIG. 3D tabulates theresults.

FIGS. 4A and 4B compare storage modulus (4A), and Tan δ (4B) at DMA forrepresentative PE-co-VAc/ZrP nanocomposites of the invention.

FIG. 5A compares tensile tests (Young's modulus and tensile strength)for representative PE-co-VAc/ZrP nanocomposites of the invention.Comparison of tensile properties containing well-exfoliated ZrP(ZrP-APTMS) and intercalated ZrP (ZrP-M1000). FIG. 5B tabulates theresults.

FIG. 6A compares barrier properties (oxygen transmission rate, OTR) ofrepresentative PE-co-VAc/ZrP nanocomposites. FIG. 6B tabulates theresults.

FIG. 7 is a schematic illustration of the preparation of representativefunctionalized exfoliated nanoplatelets of the invention, exfoliated ZrPnanoplatelets functionalized with polyethylene (PE) by ring-openingmetathesis (ROMP): PE/ZrP nanocomposites.

FIGS. 8A and 8B compare WAXD (wide-angle x-ray diffraction) of ZrPSI-ROMP (as-synthesized and hydrogenated PCO/ZrP) (8A) and direct mixwith HDPE 9003 (8B).

FIGS. 9A-9C compare rheological behavior of HDPE 9003 and HDPE/ZrPnanocomposites: complex viscosity (9A), storage modulus (9B), and Tan δ(9C).

FIG. 10 compares PE nanocomposites rheological properties. In FIG. 10,“HDPE/ZrP-ROMP” refers to a representative HDPE/ZrP nanocomposite of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides exfoliated nanoplatelets functionalizedwith a non-polar moiety, nanocomposite compositions that include thefunctionalized nanoplatelets, methods for making and usingfunctionalized nanoplatelets and nanocomposite compositions, andcompositions that include the nanocomposite compositions.

Functionalized, exfoliated nanoplatelets are disclosed that can bedispersed in solvents and polymers derived from olefinic monomers (e.g.,olefinic polymers). These nanoplatelets can be added to thermoplasticsto improve properties such as barrier to oxygen and water, as well asmechanical and other functional properties. These nanoplatelets areprepared using a two-step process. The first step is to separate(exfoliate) individual nanoplatelets from a particle containing numerousstacked nanoplatelets. This is done using a surfactant that is bound tothe surface by ionic bonds on the surface of the nanoplatelet. In thesecond step of the process, the surfactant is partially replaced orcompletely replaced with a covalently bound moiety that preventsaggregation of the nanoplatelets in solvents (e.g., non-polar,hydrophobic) and polymers. In one aspect, the invention provides acomposition comprising an exfoliated nanoplatelet functionalized with anon-polar moiety. Suitable non-polar moieties contain ahydrocarbon-chain with at least 20 carbons. In certain embodiments, thenon-polar moiety is produced by covalently coupling a silane (e.g.,having a free amine or hydroxy group) to the nanoplatelet. In otherembodiments, the non-polar moiety is produced by an olefin metathesisreaction. In further embodiments, the non-polar moiety is produced by aring-opening olefin metathesis reaction in the presence of a transitionmetal catalyst. The non-polar moiety is associated with the nanoparticleeither through covalent coupling (e.g., covalently-bound non-polarmoiety) or a hydrogen bonding interaction.

The exfoliated nanoplatelet may be derived from a natural or syntheticnanoclay. Representative natural nanoclays include montmorillonite,saponite, hectorite, mica, vermiculite, bentonite, nontronite,beidellite, volkonskoite, magadite, cloisite, kaolinite, kenyaite, andsilicate-based nanoclays. Representative synthetic nanoclays includealpha zirconium phosphate (ZrP), layered double hydroxides, and othersynthetic nanoclays as described in Utracki, L. A., et. al, Synthetic,layered nanoparticles for polymeric nanocomposites (PNCs), Polym. Adv.Technol 18: 1-36 (2007), expressly incorporated herein by reference.

In another aspect, the invention provides a film comprising exfoliatednanoplatelets functionalized with a non-polar moiety.

In a further aspect, the invention provides a nanocomposite composition,comprising a mixture of the exfoliated nanoplatelet functionalized witha non-polar moiety, as described herein, and a hydrophobic polymer, suchas a polymer derived from ethylene or propylene. Suitable polymersderived from polyethylene (PE) include copolymers, such as PE-polyvinylacetate (PE-PVAc), PE-polystyrene, PE-polypropylene, and PE-butadiene.In certain embodiments, the nanocomposite composition exhibits a modulusincrease of 100% as measured by dynamic mechanical analysis (DMA). In arelated embodiment, the invention provides a film comprising thenanocomposite composition, as described herein.

In another aspect, the invention provides a lyotropic suspension,comprising the exfoliated nanoplatelet functionalized with a non-polarmoiety, as described herein, and an organic medium (e.g., a polymer or asolvent).

In further aspects, the invention provides methods for producing anexfoliated nanoplatelet functionalized with a non-polar moietycontaining a hydrocarbon-chain with at least 20 carbons, such as apolymer, wherein the polymer has a controlled graft density andcontrolled molecular weight. The present invention also provides blendsthat, in some cases, achieve homogenized dispersion through secondarybonding, especially for copolymer types, such as PE-polyvinyl alcohol.

In certain embodiments, the blend comprises the exfoliated nanoplateletfunctionalized with a non-polar moiety, as described herein, and apolymer having ethylene or propylene units, wherein the non-polar moietyof the composition is a silane with a free amine or free hydroxy group,and wherein the polymer is modified to be absorbed to nanoplatelets bythe free amine or free hydroxy group. Useful silanes include silaneshaving amine end group, such as (3-aminopropyl)trimethoxysilane,[3-(2-aminoethylamino)propyl]trimethoxysilane,3-[2-(2-aminoethylamino)ethylamino]-propyltrimethoxysilane,[3-(methylamino)propyl]trimethoxysilane, and useful silanes includesilanes having hydroxyl amine end group, such ashydroxymethyltriethoxysilane andN-(hydroxyethyl)-N-methylaminopropyltrimethoxysilane.

In other embodiments, the blend comprises a copolymer of polyvinylacetate and polyethylene or polypropylene (e.g., PVA-co-PE or PVA-co-PP)and the exfoliated nanoplatelet functionalized with a covalently-boundnon-polar moiety, as described herein, wherein the non-polar moiety ofthe composition is a silane with a free amine or free hydroxy group.

In certain aspects, the invention provides exfoliated nanoclay (alsoreferred to herein as nanoplatelets) are covalently modified withnon-polar moieties including polyolefins (polyethylene/polypropylene)from an exfoliated state. These modified nanoplatelets are stable(remain exfoliated) in polyolefin (polyethylene/polypropylene) matricesand therefore result in improved material properties. Nanocompositesfrom these modified nanoplatelets can be synthesized easily with directmixing methods as described herein.

Example property enhancements of polyolefins with exfoliatednanoplatelets include increased oxygen and moisture barrier, andincreased modulus and increased melt strength, for materials (e.g.,films) that include the functionalized nanoplatelets. The difference inthe surface-functionalization described herein and others reportedpreviously is that the surface-functionalization of the non-polarmoieties on a representative nanoclay, zirconium phosphorus (ZrP), isdone directly from an exfoliated state with a surfactant attached to theplatelets. In the functionalized nanoplatelets, the non-polar moietiesare covalently bound to the platelet surface.

These functionalized nanoplatelet-containing compositions of theinvention are useful for packaging materials: the nanoplatelets reduceoxygen diffusion rates, and therefore allow inexpensive polyethylenefilms to compete with more expensive films such as vinylidene chloridecopolymers (e.g., SARAN®) and poly(ethylene vinyl alcohol) (EVOH). Thefunctionalized nanoplatelet can also be used as a reinforcement agent togreatly improve mechanical properties of the polymer.

For food packaging, SARAN® and EVOH have good barrier to oxygen, andcurrently share the market for food packaging for items such as meat.Both films are significantly more expensive than polyethylene film andneither SARAN® nor EVOH can be recycled, which is disadvantageous.

The methods of the invention allow for the preparation of exfoliatedfunctionalized nanoplatelets which remain exfoliated in polyolefins withsimple processing methods. This benefit has not been previously achievedand opens up many possibilities for improving polymer properties.

This disclosure describes dispersions of high aspect ratio exfoliatednanoplatelets in non-polar polymers, for example, polymers that arehydrocarbons of ethylene or propylene units, optionally in combinationwith other monomers. A key part of this invention are new nanoplateletcompositions that are functionalized with non-polar moieties. Thesenanoplatelets can be exfoliated nanoplatelets that can be dispersed insolvents and non-polar polymers. These nanoplatelets can be added tothermoplastics to improve properties such as barrier to oxygen andwater, as well as mechanical and other functional properties such asincreased modulus.

Nanoplatelet Functionalization and Nanocomposite Preparation

In the practice of the invention, nanoplatelets are prepared using atwo-step process. The first step is to separate (exfoliate) individualnanoplatelets from a particle containing numerous stacked nanoplatelets.This is done using a surfactant that is bound to the surface by ionicbonds (or coordinate bonding) on the surface of the nanoplatelet. In thesecond step of the process, the surfactant is partially replaced orcompletely replaced with a covalently bound, non-polar moiety thatprevents aggregation of the nanoplatelets in non-polar solvents andpolymers.

This two-step process converts multilayered particles with low aspectratios (<10) to individual nanoplatelets with high aspect ratios (>50).

It is desirable to exfoliate nearly all of the starting particles fortwo reasons. Non-exfoliated or partially exfoliated stacks ofnanoplatelets are undesirable because they represent a yield-loss andbecause their presence can limit the ability of the nanoplatelets toimprove properties.

There are various means to demonstrate the extent of exfoliation,including dynamic light scattering, X-ray scattering, X-ray diffraction,electron microscopy, and atomic force microscopy. Well-exfoliated,concentrated suspensions of nanoplatelets in polymers or solventsexhibit self-assembly, meaning that at least in small regions thenanoplatelets align to their neighbors. To check for self-assemblyphenomena, one simple method is to test whether the suspensions arecapable of rotating polarized light by placing a sample between a pairof polarizing films placed at 90 degrees. Samples with a highconcentration of exfoliated nanoplatelets will appear bright withregions of different colors. Another term for this behavior is liquidcrystallinity. Suspensions of nanoclays that contain an insufficientconcentration of exfoliated nanoplatelets appear dark incross-polarizers. The observance of the visible refraction of light isdependent on a number of factors, but the two most important factors arethe aspect ratio of the particles (higher is better) and theconcentration. A second test for self-assembly behavior of nanoplateletsis small-angle x-ray scattering (SAXS). Suspensions or nanocomposites ofhighly concentrated nanoplatelets that align to their neighbors willhave a preferred spacing and often a bulk orientation SAXS can detect.The spacing of the nanoplatelets will be much larger if exfoliated (4-50nm) but the actual number depends on the modifiers on the platelets aswell as solvent or polymer and the actual nanoplatelet concentration.

This invention discloses a method for preparing covalentlyfunctionalized exfoliated nanoplatelets that have the capability ofexhibiting liquid crystalline behavior at higher concentrations insolvents or can be proven to be exfoliated at lower concentrations withDLS (dynamic light scattering)/microscopy. The resulting compositionsare also described, as well as dispersions in polyolefins.

A general procedure for preparing these materials consists of two steps.In the first step, the layered nanoclay is exfoliated with a surfactantto form a suspension of high aspect ratio nanoplatelets in a solvent ormonomer. This step is performed using techniques as described in H. -J.Sue, J. Mater. Chem. A., 2015, 3, 2669-2676). In one representativeexample, a synthetic nanoclay, alpha-zirconium phosphate (referred toherein as ZrP) is exposed to a surfactant in a polar solvent. The use ofhigh-shear mixing may be advantageous. The product of this step is astable suspension of nanoplatelets (coated on both sides with thesurfactant) in a polar solvent. The nanoplatelets in layered nanoclaysare bound together by hydrogen bonds formed between hydroxyl groups(such as —P(O)OH or —SiOH). The surfactant forms an ionic bond (orcoordination bonding) with the surface hydroxyl groups and preventsaggregation of the isolated nanoplatelets. This reaction is reversible,meaning there is an equilibrium between the product, an anion-cationpair, and the neutral starting materials (the surfactant and thenanoplatelet).

Useful layered nanoclays that can be advantageously used in the methodsof the invention include natural nanoclays and synthetic nanoclays.

Representative natural nanoclays include montmorillonite, saponite,hectorite, mica, vermiculite, bentonite, nontronite, beidellite,volkonskoite, magadite, cloisite, kaolinite, kenyaite, andsilicate-based nanoclays (see U.S. Pat. No. 7,148,282).

Representative synthetic nanoclays include alpha zirconium phosphate(ZrP) (see US 20060155030A). Others synthetic nanoclays useful in theinvention include layered double hydroxides and those described inUtracki, L. A., et. al, Synthetic, layered nanoparticles for polymericnanocomposites (PNCs), Polym. Adv. Technol 18: 1-36 (2007), expresslyincorporated herein by reference.

Useful surfactants effective in the first step of the process includepolyols that have a terminal amine group. Other useful surfactantsinclude ammonium salts such as tetrabutylammonium hydroxide.

Useful solvents effective in the first step of the process includewater, methanol, ethanol, isopropanol, acetone, 2-butanone,cyclohexanone, diethyl ether, tetrahydrofuran, and glymes (such as1,2-dimethoxyethane).

The next step is removal of the solvent, in some cases the surfactant,and disperse the nanoplatelets in non-polar solvents and polymerswithout causing aggregation of the nanoplatelets. In the second step,the surfactant is partially or completely removed and replaced with anon-polar surface-active agent that is covalently bound to the surface.This is performed by reacting the product from Step 1 with a non-polarreactant that contains at least one group that is capable of forming acovalent bond with the mildly acidic surface hydroxyl groups on thesurface of the nanoplatelet (e.g., an alkoxysilane as described herein).A grafted free olefin is necessary for growing long hydrocarbon chainsusing olefin metathesis.

Reaction of the non-polar reactant with the nanoplatelet surfacehydroxyls places a non-polar moiety on the surface that is covalentlybound. It plays a key role in reducing the rate of aggregation of thenanoplatelets and can improve the dispersion with non-polar polymerssuch as polyethylene, polypropylene, and copolymers with other monomers,such as vinyl acetate, vinyl butyrate, methyl acrylate, butyl acrylate,methyl methacrylate, vinyl chloride, and acrylonitrile. As used herein,a “non-polar” moiety is defined as a material containing a hydrocarbonchain with one terminal group capable of covalently binding to thesurface of the nanoplatelets. It is possible to replace a portion of thesurfactant with one non-polar reactant, followed by replacement of allor a portion of the remaining surfactant with a second non-polarreactant. Examples of non-polar reactants include butyltrimethoxysilane,butyltriethoxysilane, dodecyltrimethoxysilane,3-aminopropyltrimethoxysilane, vinyltrimethoxysilane, 5-bicyclo[2.2.1]hept-2-enyl)triethoxysilane, 2-methylpropene, 2-methylpentene,2-methoxypropene, 2-methoxycyclohexene, 2-methoxycyclopentene.Additionally, the —P(O)OH or —SiOH groups on the surface of thenanoplatelets can be reacted with alcohols or alkyl halides underconditions that transform the OH groups to OR groups where R is anon-polar group, such as an alkyl group (for example, methyl, ethyl,butyl, hexyl, octyl, decyl, tetradecyl, hexadecyl, octadecyl), oleyl, orbenzyl group. Ethoxy and methoxy groups are interchangeable, other silylethers will also work in this step.

Ring-opening Olefin Metathesis (ROMP). Hydrocarbon oligomers andpolymers can be covalently bound to the surface using ring-openingolefin metathesis (ROMP) and a cyclic olefin. Conversion of the surfacehydroxyl groups to a non-polar moiety is beneficial for stableexfoliation of the nanoplatelets and their ability to be dispersed innon-polar solvents and polymers. The length of the non-polar moiety canbe tailored by adjusting ROMP conditions. For example, the use of excesscyclic olefin and long reaction times leads to long, high molecularweight chains. Long chains are preferred in order to prevent thenanoparticle from aggregating on mixing with non-polar polymers.However, short chains are preferable in order to minimize process timesand the consumption of cyclic olefin raw materials. Preferred chainlengths are 20 to 10,000 carbons, with 20 to 100 most preferred.

The second step, removal of the surfactant from the exfoliatednanoplatelets, can be performed in two or more substeps. This allows forthe surface of the nanoplatelets to be covered with two or moremoieties. This process involves partial removal of the surfactant andreaction with one non-polar moiety, followed by complete removal of theexcess surfactant and reaction with a second non-polar moiety. Althoughthis complicates the synthesis procedure, it has the advantage that thesurface characteristics of the nanoplatelets can be adjusted to maximizethe compatibility when mixed with polyolefins. In this way ananocomposite with optimal performance can be obtained on mixing thenanoplatelets with a non-polar polymer. It may be possible to prepare ananoplatelet with mixed covalently-bound non-polar moieties in one stepby starting with a mixture of reactants and controlling the compositionof the product by changing the molar ratio of the reactants and/orrelying on reaction rate differences.

Surface-initiated ROMP (SI-ROMP) has previously been achieved withnanofillers by grafting a norbornyl or vinyl group on the filler surfacethat can immobilize Grubb's catalyst and initiate ROMP (ACS MacroLetters 8.3 (2019): 228-232; Macromolecules 46.23 (2013): 9324-9332; andPolymer 153 (2018): 287-294) to provide the functionalizednanoplatelets. Nanofillers studied thus far have been spherical(silica), 2D nanoplatelets (montmorillonite (MMT)), and carbonnanotubes. The polyethylene chains on the silica surface were shown toimprove dispersion of the particles when mixed with neat high-densitypolyethylene (HDPE). For 2D nanoplatelets, MMT was intercalated with anorbornyl functional group bound to the surface via an ionicinteraction. Mechanical properties of the nanocomposite weresignificantly enhanced after the polyolefin was grown from the MMTsurface. However, the SI-ROMP reported currently based on 2Dnanoplatelets was induced from an intercalated structure. SI-ROMP canincrease MMT interlayer distance, but cannot achieve exfoliation of thenanoplatelets after ROMP, which limits the nanocomposites propertyenhancement.

In certain aspects, the invention provides a nanoplatelet withcovalently bound norbornyl functionality directly on an exfoliated ZrPsurface, which can be used to generate the stable covalent grafting ofpolyethylene. The polyethylene (PE)-grafted ZrP can be directly mixed insolvent with neat HDPE and maintain exfoliation after drying.

Representative Functionalized Exfoliated Nanoplatelets andNanocomposites Example 1 describes a procedure for preparingrepresentative functionalized exfoliated nanoplatelets of the invention,PE-co-PVA/ZrP nanocomposites. FIG. 1A is a schematic illustration of thepreparation of a representative nanoplatelet functionalized with analkoxysilane having a free amine (APTMS). FIG. 1B is a schematicillustration of the preparation of a representative nanocomposite of theinvention, PE-co-VAc/ZrP, from nanoplatelet functionalization with analkoxysilane having a free amine (APTMS). FIG. 2 is a schematicillustration of the interaction between PE-co-VAc with the free amine ofthe silane covalently coupled to the nanoplatelet for the nanocompositeshown in FIG. 1A.

ZrP was functionalized from exfoliated state by secondary modifiers thatprovide interaction sites with polymer while maintaining ZrPexfoliation. APTMS grafts on the ZrP surface and partially replaces thesurfactant (M1000). ZrP remains exfoliated after

APTMS grafting (z-Avg=95 nm in THF and toluene). Assuming all APTMS hasbeen grafted at the low ratio to the POH of 10%. Combining FTIR (fouriertransform infrared) and TGA results, grafting ratio of APTMS and M1000to the POH are 10% and 20%, respectively.

PE-co-VAc has various industrial applications; some requiring high meltstrength, excellent tensile. However, it is well known to be a pooroxygen barrier. PE-co-VAc/α-ZrP nanocomposites improve PE-co-VAcmechanical and barrier properties. However, poor dispersion of α-ZrP inPE-co-VAc limits property enhancement. Exfoliated α-ZrP with aminefunctionalities generates hydrogen bonding with the acetate functionalgroup on the PE-co-VAc that stabilizes α-ZrP exfoliation in PE-co-VAcmatrix. PE-co-VAc mechanical properties are significantly improved byintroducing exfoliated functionalized α-ZrP.

AFM (atomic force microscopy) and DLS confirmed the solvent effect onZrP exfoliation in the PE-co-VAc copolymer. Amine functionality lead toincrease in ZrP d-spacing as confirmed by WAXD and SAXS. TEM(transmission electron microscopy) confirmed exfoliated ZrPnanoplatelets in PE-co-VAc matrix.

Upon interaction between ZrP and polymer, polymer serves as a linkerbetween ZrP platelets, which can lead to stacking of ZrP platelets(believed to be the large particles seen with DLS). The hydrogen bondingcapability of solvents determines whether polymer can be coated on ZrPsurface (non-polar solvents such as toluene provide for coating; polarsolvents such as tetrahydrofuran (THF) prevent effective coating).

PE-co-VAc generates denser coating on ZrP (more hydrogen bonding sites)in toluene environment than THF. Densely coated PE-co-VAc on ZrP willnot affect ZrP d-spacing after heating above the melting temperature ofthe nanocomposite.

FIGS. 3A-3C compare of rheology properties [complex viscosity (3A),storage modulus (3B), and Tan δ (3C)] containing well-exfoliated ZrP(ZrP-APTMS) and intercalated ZrP (ZrP-M1000). Well-exfoliated ZrP andinteraction between APTMS and polymer can significantly increase meltstate viscosity and storage modulus. FIG. 3D tabulates the results.

FIGS. 4A and 4B compare storage modulus (4A), and Tan δ (4B) at DMA forrepresentative PE-co-VAc/ZrP nanocomposites of the invention. ExfoliatedZrP-APTMS increases G′ compared to neat PE-co-VAc matrix. Poorlyexfoliated ZrP-M1000 and free M1000 remaining in the system deteriorateG′ and increase Tan δ.

FIG. 5A compares tensile tests for representative PE-co-VAc/ZrPnanocomposites of the invention. Comparison of tensile propertiescontaining well-exfoliated ZrP (ZrP-APTMS) and intercalated ZrP(ZrP-M1000). Young's Modulus:

well-exfoliated ZrP with high surface area and interaction withPE-co-VAc significantly increases Young's modulus. Intercalated ZrP inPE-co-VAc only slightly increases Young's modulus. Tensile strength:better dispersed and exfoliated ZrP in PE-co-VAc leads to higher tensilestrength. FIG. 5B tabulates the results.

FIG. 6A compares barrier properties (oxygen transmission rate, OTR) ofrepresentative PE-co-VAc/ZrP nanocomposites. PE-co-VAc has a poorbarrier property against oxygen. OTR value of PE-co-VAc/ZrPnanocomposite is decreased by 30% after 10 wt. % of ZrP loading (withM1000). M1000-free ZrP enhances barrier property more effectively at 40%reduction after only 2.5 wt. % addition. FIG. 6B tabulates the results.

Example 2 describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with polyethylene (PE) by ring-opening metathesis (ROMP):PE/ZrP nanocomposites. The preparation is schematically illustrated inFIG. 7.

FIG. 7 is a schematic illustration of the preparation of representativefunctionalized exfoliated nanoplatelets of the invention, exfoliated ZrPnanoplatelets functionalized with polyethylene (PE) by ring-openingmetathesis (ROMP): PE/ZrP nanocomposites.

For ring-opening metathesis (ROMP), exfoliated ZrP nanoplatelets arefunctionalized with an alkene that is suitable for ROMP. In certainembodiments, the alkene is a vinyl group that is covalently coupled tothe nanoplatelet by reaction of the nanoplatelet with a vinyl silane(e.g., vinyl trimethoxysilane, VTMS). The functionalized nanoplatelet isthen subject to ROMP using a cycloolefin, such as cyclooctene, using aGrubb's catalyst. The result is exfoliated ZrP nanoplateletsfunctionalized with polyethylene (PE): PE/ZrP nanocomposites.

FIG. 7 illustrates ZrP-NTES surface-initiated ROMP from ZrP-NTES-ETMS.Norbornyl silane (e.g., NTES) provides the benefit of using a norbornylgroup rather than a simple alkene group (e.g., vinyl) related to therelief of ring strain after the catalyst reacts with the norbornenemoiety generates an essentially irreversible tether. Polycyclooctene(PCO) grafting density can be alternated by NTES grafting ratio.

Referring to FIG. 7, NTES is reacted with ZrP and then further reactedwith ethyl trimethoxysilane (ETMS). In the two-step reaction, NTES isgrafted on then ZrP surface followed by addition of ETMS at highertemperature to remove M1000 and keep ZrP exfoliated. Silanization wasconfirmed by FTIR and TGA. NTES reacted at relative low temperature andits low grafting ratio did not effectively remove M1000. By introducingETMS at elevated temperature, M1000 was effectively removed, which caneliminate the yellowing previously seen at high temperatures and improvemechanical properties. ZrP-NTES-ETMS remains exfoliated in THF orxylene.

The silane-modified ZrP was then subject to surface-initiated ROMP(Grubb's 3^(rd) catalyst followed by cyclooctene and hydrogenation).After ROMP, solution was first passed through Al₂O₃ column to remove thecatalyst. Then, methanol was used to separate unreacted ZrP and low MWPCO from PCO-grafted ZrP. ROMP at 10 and 15 wt % loading, ZrP remainsexfoliated in THF before and after ROMP. After ROMP, lyotropic PCO/ZrP(15 wt %) liquid crystals were observed under cross-polarized light.

FTIR confirmed the PCO grafting on ZrP surface. ZrP induced ROMP fromits surface and edges. ZrP remains exfoliated and PCO growspreferentially on ZrP edges. After hydrogenation, PCO-grafted ZrP wasconverted into PE-grafted ZrP.

Example 3 describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with high density polyethylene (HDPE): HDPE/ZrPnanocomposites.

In certain embodiments, following PCO/ZrP hydrogenation, PE/ZrPnanocomposites can be direct mixed with neat HDPE. HDPE has variousindustrial applications but has a high oxygen transmission rate;increasing its barrier property can extend HDPE applications. α-ZrP is asynthetic 2D layered material that can be readily exfoliated andmodified with desired functionalities. PE/α-ZrP nanocomposites are shownherein to improve HDPE mechanical and barrier properties. However, poordispersion of α-ZrP in HDPE limits property enhancement. Exfoliatedα-ZrP with surface grafted PE can improve ZrP miscibility in HDPE matrixand induce co-crystallization between neat HDPE and grafted PE. As shownherein, PE mechanical properties are significantly improved byintroducing and stabilizing exfoliated α-ZrP.

PCO can be hydrogenated into HDPE by noncatalytic hydrogenation. GraftedPE and neat HDPE can co-crystallized. PCO with higher MW has highercrystallization and melting temperature. Longer polymer chain can betterco-crystallize with neat HDPE and does not affect the crystallinity.

FIGS. 8A and 8B compare WAXD of ZrP SI-ROMP (as-synthesized andhydrogenated PCO/ZrP) (8A) and direct mix with HDPE 9003 (8B).

PCO grafted ZrP after hydrogenation did not form detectable stackingstructure in HDPE 9003. Monoclinic PE crystalline structure wasobserved. After rheology measurement at 205° C., ZrP did notre-aggregate.

FIGS. 9A-9C compare rheological behavior of HDPE 9003 and HDPE/ZrPnanocomposites: complex viscosity (9A), storage modulus (9B), and Tan δ(9C). Rheology behavior at low frequency: ZrP significantly increasedHDPE viscosity and storage modulus at 1.5 wt % loading. Rheologybehavior at high frequency: HDPE/ZrP nanocomposites viscosity andstorage modulus decreased to lower then HDPE believed to be from thepresence of M1000. Introducing ZrP in HDPE leads to lower tan δ value atfrequency 0.1-100 rad/s.

FIG. 10 compares PE nanocomposites rheological properties. In FIG. 10,“HDPE/ZrP-ROMP” refers to a representative HDPE/ZrP nanocomposite of theinvention. As shown in FIG. 10, compared to the recently reported HDPEnanocomposites melt strength studies, PE/ZrP (via ROMP) having largeaspect ratio and potentially good exfoliation and dispersion cansignificantly increase composites melt viscosity and storage modulus atlow ZrP weight fraction.

Example 4 describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with polycyclooctene (PCO) by ring-opening metathesis(ROMP): PCO/ZrP nanocomposites.

As used herein, the term “about” refers to ±5% of the specified value.

The following examples are provided for the purpose of illustrating, notlimiting, the invention.

EXAMPLES Example 1 Preparation of Representative FunctionalizedExfoliated Nanoplatelets: PE-co-PVA/ZrP Nanocomposites

This example describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with a copolymer (PE-co-PVA): PE-co-PVA/ZrPnanocomposites. The preparation is schematically illustrated in FIG. 1B.

Step 1 (exfoliation). ZrP was prepared according to a publishedprocedure (H. -J. Sue, J. Mater. Chem. A., 2015, 3, 2669-2676). Theexfoliation of ZrP was carried out using JEFFAMINE® M1000 (a copolymerof ethylene oxide and propylene oxide with an amine group at one endonly). For dispersion, 6 g of ZrP mixed with 210 ml of acetone in a 500ml round bottom flask and sonicated for 30 minutes. A JEFFAMINE® M1000solution in acetone (0.6 g/ml) was added (33 mL) dropwise to thestirring ZrP mixture. This dispersion was allowed to stir for 12 h. Thedispersion was sonicated for 60 min followed by centrifugation at 10,000rpm for 30 min. The sediment was removed leaving a clear suspensioncontaining exfoliated ZrP-M1000 and excess JEFFAMINE® M1000. The excessJEFFAMINE® M1000 was removed using dialysis in acetone. IR (cm-1): 2866broad (C—H). TGA (air) mass loss 190-420° C., 51.33 wt %.

Preparation of ZrP-M1000-APTMS. A portion of ZrP-M1000 (ZrP 30 mg),prepared as described above, was re-dispersed in 20 mL THF. The ZrPsolution was warmed in a 60° C. oil bath. A 0.7 mg/mL solution of(3-aminopropyl)trimethoxysilane (APTMS) in THF was prepared. A volume of5 mL of APTMS solution (20 mol % to ZrP) was added dropwise into the ZrPsolution. The solution was allowed to stir overnight. The as-synthesizedZrP-APTMS was purified by adding hexane and collect the sediment incentrifuge at 3000 rpm for 2 minutes. The purified ZrP-APTMS sedimentwas re-dispersed into 20 mL toluene.

Preparation of polyethylene-co-polyvinyl acetate (PE-co-VAc)/ZrPnanocomposite. To prepare PE-co-VAc/ZrP nanocomposites at 10 wt % ofZrP, a solution mixing method was applied. The purified ZrP-APTMSsolution in toluene, prepared from ZrP-APTMS as described above, wasstirred and pre-heated at 80° C. in an oil bath. PE-co-VAc pellets (0.27g) were dissolved in 10 mL of toluene at 80° C. and the solution wasadded dropwise into the ZrP-APTMS solution while stirring. The mixturewas stirred for 1 hour. Solvent was removed by rotary evaporator to givea transparent gel which was dried in a vacuum oven. The PE-co-VAc/ZrPnanocomposite (10 wt %) was formed into a film using a hot press at 100°C. and 1200 kg. AFM of diluted PE-co-VAc/ZrP solution showed polymerimmobilized on exfoliated ZrP surface (ZrP-APTMS thickness 2 nm,PE-co-VAc/ZrP-APTMS 20 wt % thickness 10 nm). DLS (correlationcoefficient) corresponded with AFM results. WAXD and SAXS showed thed-spacing of ZrP in PE-co-VAc matrix was 6 nm at ZrP 10 wt %. TEM and OM(optical microscopy) confirmed the good dispersion and exfoliation ofZrP in PE-co-VAc at 10 wt %. Introducing exfoliated ZrP in PE-co-VAcsignificantly increased polymer melt strength, Young's modulus, andslightly decreased the polymer crystallinity. Crystallinity ofPE-co-VAc/ZrP nanocomposites slightly decreased from 9% (neat PE-co-VAc)to 7% at 10 wt % ZrP loading. Compared to neat PE-co-VAc, PE-co-VAc/ZrPnanocomposites viscosity (100° C., 0.1 rad/s) increased to 1.6 and 3.6times at 3 wt % and 10 wt %, respectively. Storage modulus at the samecondition increased 2 and 6 times at 3 wt % and 10 wt %, respectively.Tan δ significantly decreased with the introduction of exfoliated ZrP.DMA test from −135° C. to 50° C. showed an increase in storage modulusand a good damping behavior around room temperature. Young's modulusincreased 3.6 times with respect to neat PE-co-VAc at 10 wt % ZrPloading.

Example 2 Preparation of Representative Functionalized ExfoliatedNanoplatelets: PE/ZrP Nanocomposites

This example describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with polyethylene (PE) by ring-opening metathesis (ROMP):PE/ZrP nanocomposites. The preparation is schematically illustrated inFIG. 7.

ZrP-NTES-ETMS preparation. A portion of the ZrP-M1000 (ZrP 30 mg),prepared as described above, was concentrated to a gel in a rotaryevaporator and re-dispersed in 20 mL xylene. The ZrP-M1000 solution wasthen warmed to 60° C. in an oil bath. Norbornyl silane,(5-bicyclo[2.2.1]hept-2-enyl)triethoxysilane (NTES) was used tofunctionalize ZrP. A 15 mg/mL solution of NTES in xylene was prepared.This solution (3.4 mL, 2:1 mol ratio NTES:ZrP) was added to theZrP-M1000 solution and was stirred overnight. The as-synthesizedZrP-NTES solution was further reacted with ethyl trimethoxylsilane(ETMS, 3:1 mol ratio vs ZrP) at 100° C. in xylene for 24 hours to removethe JEFFAMINE® M1000 surfactant. The resultant ZrP-NTES-ETMS was firstpurified by adding hexane and the ZrP sediment was isolated using acentrifuge (3000 rpm). This purification step was repeated 3 times toremove non-grafted NTES and ETMS. Silica gel was introduced to furtherremove free JEFFAMINE® M1000. The upper solution was collected andcentrifuged for 10 min (10,000 rpm) to remove both the remaining silicaand non-exfoliated ZrP. Finally, THF was added to the ZrP-NTES-ETMSuntil a concentration of 1.5 mg/mL was reached.

DLS (Z avg) of purified ZrP-NTES-ETMS is 95 nm in THF. TGA (N₂) massloss from 300-450° C., 42 wt %.

ZrP surface-initiated Ring-Opening Metathesis Polymerization (SI-ROMP).Cyclooctene was first passed through alumina columns to removestabilizers before use. Grubb's 3rd generation olefin ring-openingmetathesis catalyst(dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)bis(3-bromopyridine)ruthenium(II)) was used as received. The entire processwas performed under a nitrogen atmosphere. A Schlenk flask was firstdegassed and filled with nitrogen. ZrP-NTES-ETMS (30 mg ZrP), preparedas described above, in THF solution was added, and 8.5 mg of theruthenium catalyst was added in 0.5 mL THF. The solution was stirred for20 min. Cyclooctene (0.12 g) was dissolved in 0.5 mL THF andfreeze-pump-thaw was used to remove oxygen. After the dropwise additionof cyclooctene the resulting solution was stirred at room temperaturefor 120 minutes. Then 0.2 mL of ethyl vinyl ether was added to thereaction to quench the ROMP with stirring for 30 min. The as-synthesizedZrP-polycyclooctene (PCO) solution was passed through an alumina columnto remove the catalyst. The solution was then concentrated and the ZrPwas washed with methanol to remove non-reacted cyclooctene and possibleoligomers. The PCO grafted ZrP was exfoliated after redispersing in THF,with a hydrodynamic size of 95 nm measured by DLS. The FTIR revealedstrong peaks at 2921 cm⁻¹(C—H), 2845 cm⁻¹ (C—H) and no intercalationpeaks from 2-10° in WAXD. [110] and [201] PCO crystalline peaks can beobserved at 20=20.1° and 23.9°. Melting and crystallization temperatureswere 60° C. and 40° C., respectively based on DSC results with atemperature ramp of 10° C./min.

Conversion of PCO-grafted ZrP into polyethylene-grafted ZrP. A 250 mL3-neck flask Schlenk flask was first degassed and filled with nitrogenusing a Schlenk line. The PCO/ZrP (30 mg ZrP), prepared as describedabove, was dissolved into 30 mL xylene then transferred into the Schlenkflask along with p-toluenesulfonyl hydrazide (0.2 g, 1 eq. with respectto the olefin in the polymer). The flask was equipped with a refluxcondenser, a rubber stopper and the other neck was connected tonitrogen. A syringe was used to transfer the PCO/ZrP solution into theflask which was then heated in a 135° C. oil bath. Then, 0.2 gtributylamine (1 eq. to polymer) was introduced to the stirring solutiondropwise via a syringe. This mixture was heated and stirred for 6 hours,then allowed to cool. The product (polyethylene-grafted ZrP) wasprecipitated into methanol. The sediment was collected by centrifuge at5000 rpm. The solid product was then washed three times with methanol.

The crystallization temperature and melting temperature were 112° C. and132° C., respectively, based on DSC results with a temperature ramp of10° C./min. ZrP with covalently-bound hydrogenated PCO didco-crystallize with neat HDPE. ZrP remained exfoliated afterhydrogenation and PE [110] and [200] crystalline peaks were observed inWAXD at 20=21.5° and 23.9°.

Example 3 Preparation of Representative Functionalized ExfoliatedNanoplatelets: HDPE/ZrP Nanocomposites

This example describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with high density polyethylene (HDPE): HDPE/ZrPnanocomposites.

Direct mix HDPE grafted ZrP with neat HDPE. To prepare HDPE/ZrPnanocomposites with 5 wt % ZrP, a solution mixing method was applied.Commercially available HDPE (0.45 g, Mn 10,000 Daltons, polydispersityindex of 15 from Formosa Plastics) was dissolved in 30 mL xylene at 120°C. for 30 min Polyethylene-grafted ZrP (ZrP 30 mg), prepared asdescribed in Example 2 (the polyethylene grafted ZrP prepared asdescribed in Example 2 was further diluted in neat HDPE), was dissolvedin 20 mL xylene at 120° C. for 30 min. A glass pipet was used totransfer the hot HDPE solution into the PE/ZrP solution with stirring.The mixture was heated and stirred for 1 hour. The solution was dried at60° C. overnight and then further dried at 120° C. in a vacuum oven. Theproduct, a HDPE/ZrP nanocomposite, was then hot-pressed into a film.

No ZrP intercalation peaks appeared in WAXD. Crystallinity of the PE/ZrPnanocomposites is 77% at 1.5 wt % ZrP loading, with respect to 78% ofthe neat HDPE. The viscosity of the composite as measured at 205° C. and0.1 rad/s was 67 kPa vs 33 kPa for the starting HDPE. The storagemodulus increased under the same conditions was 5.0 kPa, vs 1.5 kPa forthe starting HDPE.

Example 4 Preparation of Representative Functionalized ExfoliatedNanoplatelets: PCO/ZrP Nanocomposites

This example describes the preparation of representative functionalizedexfoliated nanoplatelets of the invention, exfoliated ZrP nanoplateletsfunctionalized with polycyclooctene (PCO) by ring-opening metathesis(ROMP): PCO/ZrP nanocomposites.

ZrP functionalization procedure (0.5 g ZrP, 10 mol % norbornylgrafting). A suspension of 16.7 mL ZrP-M1000 in acetone (ZrPconcentration: 30 mg/mL in acetone) was added to a round bottom flaskand the acetone was removed using rotary evaporator. The solid was thensuspended in 80 mL xylene. This suspension was heated to 80° C. in anoil bath under a nitrogen atmosphere to prevent ZrP aggregation causedby M1000 oxidation.

To a vial was added 40 mg of 5-bicyclo[2.2.1]hept-2-enyl) ethyltrimethoxysilane (NTMS) and 2 mL xylene. This solution was added to thesuspension of ZrP-M1000 and allowed to react for 24 hours.

A solution of 6.25 g octadecyl trimethoxysilane (ODMS) in 5 mL xylenewas prepared. This solution was added dropwise using a syringe to theZrP-M1000-NTMS suspension. Heating was continued for 24 hours. ODMSgrafting introduces the long alkyl chain on ZrP surface to increase ZrPhydrophobicity and prevent ZrP aggregation after subsequent catalystimmobilization.

A solution of 5 g ethyl trimethoxysilane (ETMS) in 5 mL xylene was addedto the ZrP-M1000-NTMS-ODMS solution, and the reaction temperature wasincreased to 110° C. and react in air for 24 hours to fully remove theZrP bound M1000. This solution was allowed to cool, and 5 g silica gelwas added to fully absorb free M1000. After the silica gel fully settleddown, the upper ZrP solution was collected and then precipitated inexcess hexane and centrifuge at 5000 rpm for 5 minutes then re-dissolvein THF. The hexane purification is repeated 3 times to remove theunreacted silanes.

ZrP SI-ROMP procedure (30 mg ZrP, graft density 10 mol %, MW=50,000g/mol). Grubb's 3^(rd) catalyst (dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)bis(3-bromopyridine)ruthenium (II)) (1 molar equiv. to the NTMS) was added to a Schlenkflask, which was degassed and purged with nitrogen.

Add 3 mL of THF into Schlenk flask to dissolve the catalyst. Thissolution was purged with nitrogen to 3 mL of ZrP solution (ZrPconcentration 10 mg/mL), then transfer the ZrP solution into the Schlenkflask with catalyst solution (ZrP-catalyst concentration=5 mg/mL). Thiswas stirred for 15 minutes to fully immobilize the catalyst onto the ZrPsurface.

In the meantime, purify cyclooctene monomer by passing through a basicAl₂O₃ column to remove the impurities and stabilizers. A monomersolution with 0.5 g (0.59 mL) cyclooctene, 4.5 mL THF (cyclooctene 1mol/L), 0.1 g butylated hydroxytoluene (BHT) (10 mol. % to monomer) wasprepared.

Hexane (20 mL) was added to a centrifuge tube and purged with nitrogen.Transfer the ZrP-catalyst solution into the hexane and centrifuge at5000 rpm for 4 minutes to remove the free catalyst. The upper solutionwas discarded and re-dissolved in 6 mL THF. After purging with N₂ for 2min, the solution was transferred to the degassed Schlenk flask using asyringe. Purge N₂ into the prepared monomer solution for 2 minutes, thentransfer into the stirring ZrP-catalyst solution in Schlenk flask. Thiswas allowed to react for 2 hours at room temperature. Add 1 mL ethylvinyl ether to terminate the polymerization and remove the catalyst fromthe chain ends. Stir for 15 minutes. Dilute and precipitate theZrP-g-PCO (polycyclooctene) solution in methanol and wash 3 times toremove the catalyst and the unreacted monomers or oligomers. TheZrP-g-PCO was re-dissolved in xylene at a concentration of (PCO 5 mg/mL)and stored in a freezer (−20° C.) to prevent PCO crosslinking.

Hydrogenation procedure. The ZrP-g-PCO solution was transferred to a3-neck flask at room temperature with stirring and nitrogen flow for 30min. The three necks were connected to nitrogen, reflux condenser andsealed with rubber stopper.

To this flask was added 1 g BHT (1 molar equiv. to double bond), 2.5 gp-toluenesulfonyl hydrazide (TSH) (3 molar equiv. to double bond), 5 gtributylamine (TBA) (6.4 mL) (6 molar equiv. to double bond). Thissolution was heated to 115° C. and stirred for 2 hours. After allowingthe solution to cool to room temperature, it was precipitated withmethanol and centrifuged at 7000 rpm for 5 min and collect the sediment.Byproducts from the hydrogenation were removed together with the uppersolution. This methanol purification was repeated 3 times.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A composition,comprising an exfoliated nanoplatelet functionalized with a non-polarmoiety.
 2. The composition of claim 1, wherein the non-polar moiety isassociated with the platelet through a hydrogen bonding interaction. 3.The composition of claim 1, wherein the non-polar moiety is covalentlycoupled to the nanoplatelet.
 4. The composition of claim 1, wherein thenon-polar moiety is associated with the platelet through a silane thatis covalently coupled to the platelet.
 5. The composition of claim 1,wherein the non-polar moiety contains a hydrocarbon chain with at least20 carbon atoms.
 6. The composition of claim 1, wherein the non-polarmoiety is produced by an olefin metathesis reaction.
 7. The compositionof claim 1, wherein the non-polar moiety is produced by a ring-openingolefin metathesis reaction in the presence of a transition metalcatalyst.
 8. The composition of claim 7, wherein the ring-opening olefinmetathesis reaction is a reaction between an alkene covalently coupledto the platelet and a cycloalkene, wherein the alkene is selected fromthe group consisting of a vinyl group and cyclic and polycyclic olefins.9. The composition of claim 1, wherein the exfoliated nanoplatelet isderived from a natural or synthetic nanoclay.
 10. A film, comprising thecomposition of claim
 1. 11. A nanocomposite composition, comprising amixture of the composition of claim 1 and a polymer derived fromethylene or propylene.
 12. The nanocomposite composition of claim 11that exhibits a modulus increase of 100% relative to the polymercontaining no filler, as measured by dynamic mechanical analysis. 13.The nanocomposite composition of claim 11 that exhibits a modulusincrease of 150% relative to the polymer containing no filler, asmeasured by tensile test.
 14. A film, comprising the nanocompositecomposition of claim
 11. 15. A lyotropic suspension, comprising thecomposition of claim 1 and an organic medium.
 16. A method for producinga functionalized exfoliated nanoplatelet, comprising: (a) covalentlycoupling a silane to an exfoliated nanoplatelet, wherein the silane hasa functional group for associating a polymer to the nanoplatelet; and(b) associating a polymer comprising a hydrocarbon-chain with at least20 carbons to the nanoplatelet through the functional group of thesilane.
 17. The method of claim 16, wherein the functional group of thesilane is a hydroxy group or an amine group and the polymer.
 18. Themethod of claim 16, wherein the functional group of the silane is analkene group.
 19. The method of claim 16, wherein the polymer is apolymer derived from ethylene or propylene.
 20. A method for producingan exfoliated nanoplatelet functionalized with a covalently-boundnon-polar moiety containing a hydrocarbon-chain with at least 20carbons, wherein the polymer has a controlled graft density andcontrolled molecular weight.